/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.jasper.el;

import org.apache.jasper.Constants;

import javax.el.*;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;

/**
 * Implementation of ELContext
 *
 * @author Jacob Hookom
 */
public class ELContextImpl extends ELContext {

	private static final FunctionMapper NullFunctionMapper = new FunctionMapper() {
		@Override
		public Method resolveFunction(String prefix, String localName) {
			return null;
		}
	};
	private static final ELResolver DefaultResolver;

	static {
		if (Constants.IS_SECURITY_ENABLED) {
			DefaultResolver = null;
		} else {
			DefaultResolver = new CompositeELResolver();
			((CompositeELResolver) DefaultResolver).add(new MapELResolver());
			((CompositeELResolver) DefaultResolver).add(new ResourceBundleELResolver());
			((CompositeELResolver) DefaultResolver).add(new ListELResolver());
			((CompositeELResolver) DefaultResolver).add(new ArrayELResolver());
			((CompositeELResolver) DefaultResolver).add(new BeanELResolver());
		}
	}

	private final ELResolver resolver;
	private FunctionMapper functionMapper = NullFunctionMapper;
	private VariableMapper variableMapper;

	public ELContextImpl() {
		this(getDefaultResolver());
	}

	public ELContextImpl(ELResolver resolver) {
		this.resolver = resolver;
	}

	public static ELResolver getDefaultResolver() {
		if (Constants.IS_SECURITY_ENABLED) {
			CompositeELResolver defaultResolver = new CompositeELResolver();
			defaultResolver.add(new MapELResolver());
			defaultResolver.add(new ResourceBundleELResolver());
			defaultResolver.add(new ListELResolver());
			defaultResolver.add(new ArrayELResolver());
			defaultResolver.add(new BeanELResolver());
			return defaultResolver;
		} else {
			return DefaultResolver;
		}
	}

	@Override
	public ELResolver getELResolver() {
		return this.resolver;
	}

	@Override
	public FunctionMapper getFunctionMapper() {
		return this.functionMapper;
	}

	public void setFunctionMapper(FunctionMapper functionMapper) {
		this.functionMapper = functionMapper;
	}

	@Override
	public VariableMapper getVariableMapper() {
		if (this.variableMapper == null) {
			this.variableMapper = new VariableMapperImpl();
		}
		return this.variableMapper;
	}

	public void setVariableMapper(VariableMapper variableMapper) {
		this.variableMapper = variableMapper;
	}

	private static final class VariableMapperImpl extends VariableMapper {

		private Map<String, ValueExpression> vars;

		@Override
		public ValueExpression resolveVariable(String variable) {
			if (vars == null) {
				return null;
			}
			return vars.get(variable);
		}

		@Override
		public ValueExpression setVariable(String variable,
		                                   ValueExpression expression) {
			if (vars == null)
				vars = new HashMap<String, ValueExpression>();
			return vars.put(variable, expression);
		}

	}
}
